In a letter, Merrill said he plans his retirement to be effective Feb. 1, 2018.

Merrill said he had "a whirlwind of emotions about this decision."

In his retirement letter, Merrill added:

"I have enjoyed, beyond measure, my twenty years plus serving the adults and children of Wake County. While we have made much progress and have many accomplishments to which we can point, there always is more work to be done."

Merrill did not give specific reasons for the timing of his decision. He said he believed the schools were "in a good place" but cited challenges such as growth, funding and legislative mandates.

"It is with mixed emotions I accept Dr. Merrill's retirement announcement," said Monika Johnson-Hostler, WCPSS Board of Education Chair. "While we aren't ready for his retirement, we recognize as a thoughtful leader he has given this significant thought and planning."

She also said Merrill was "ready to spend time and enjoy his family" and that the board supported that decision.

Johnson-Hostler said the board will begin the search for a new superintendent in the upcoming weeks.